The objective of the currently ongoing and of additional, projected experiments is to determine the extent to which arousal and associative learning affect the responses of individual neurons in primate somatosensory cortex to peripheral cutaneous stimuli. The behavioral task situations are of two kinds: a) conditioned negative variation paradigms in which the cutaneous stimuli serve as behaviorally neutral test probes; and b) stimulus discrimination paradigms in which the direction of moving cutaneous stimuli are the discriminative stimuli. Stimulus responses and neural activity in the intertrial periods are analyzed quantitatively for their statistical properties. These experiments are expected to enable the characterization of changes in neural activity which are associated with arousal (or expectancy) on the one hand, and associative learning on the other. Once these baseline data are in hand, the effect of behavior altering pharmacological agents (phencycidine, phenothiazines) will be examined for their effects on the associated behavioral and neual changes.